So, almost everything I have read uses that example as the time when you should do any serious work on the tree. But, I'm wondering if this makes sense from a biological stand point. I know that a few of the people who post on this forum have an advance understanding of plant biology, so I figured I'd ask. It just doesn't make sense to me to remove a branch, or collect a plant after the energy is beginning to move to the outer areas of the plant. Wouldn't it be better to hard prune the branch while the plant is still dormant? Or, perhaps even better, isolate the branch that you want to remove, and then simply pinch of all of the buds, and force that energy to find a new avenue of growth somewhere else on the tree? Then, remove the branch after a good flush of growth? I mean, rather than simply cutting off the branches that are starting to be fed by the trees energy store.

I don't know if I really qualify as being highly knowledgeable on plant physiology but what has helped me make better decisions on when and how to apply technique was to do some basic study of "modern" writings on just that: plant physiology. I found what I understood and was taught was often simply wrong. Basic understanding of tree structures and how they work is not easy to synopsize--it would be long and tedious discussion. The analogy you point out though could be commented on and it has some credence. The issue, I believe, is to take in account the hormonal signals for energy that the branch and buds give and the effects of the root response--especially considering the seasonal stored energy.

Despite the descriptions of 'energy flow' that continue to be promulgated, all energy/food for the tree is manufactured by the foliage. Every branch makes enough carbohydrates for its own needs plus some for the roots and trunk. All the energy needed for deciduous trees to start up in the spring is stored as starches in the leaf buds. A bit more is stored in other (vascular cambium and ray parenchyma) living cells. In all trees, all food stored locally, even conifers. If you prune in dormancy, it does not change the energy storage in the rest of the tree.

Water and nutrients are drawn up the tree through the xylem (wood) by transpiration (i.e., it is sucked up the tree through the little xylem 'soda staws'). Therefore, if you remove all buds on a deciduous branch, it is dead because no leaves will emerge in spring to draw water and nutrients.

The basic phytohormone do-loop in trees is the foliage makes auxin that flows downward in the phloem to the roots. The roots make cytokinins that signal nitrogen is available and stimulate foliage growth. Auxin induces the cambium to make more xylem and phloem and to grow more roots. Auxin, however, also acts as a defoliant and deactivates 'down stream' buds closer to the trunk/roots. Pruning the apical foliage from a deciduous branch AFTER it has leafed out collapses the auxin flow and releases interior buds (causes back budding). Candle pruning and needle plucking similarly stimulate back budding in conifers because it collapses the auxin flow (though needle plucking is mostly for getting light to the interior of the tree to help stimulate bud release). The auxin and cytokinin levels are both low during dormancy, so pruning during dormancy has no direct back budding effect.

Trees effectively stop growing when the air temperatures are above ca. 95F because the tree burns more energy than can be captured by the foliage (respiration outpaces photosynthesis). Roots don't grow at temperatures above roughly 95F and begin to die at soil temperatures above 105F (supraoptimal root temperatures). Since something like 95% of the water drawn in by the roots is lost to transpiration, it is most important to keep your soil temperatures below 105F. Roots adsorb water and nutrients primarily through microscopic root hairs. Root hairs are elogations of individual cells on the surface of the root near the tip of the root. Each hair lasts for only a matter of days. New hairs are made as the root tip extends/advances. If the roots aren't growing there soon will be no hairs and the tree will get very sick if not die (there is weak absorption elsewhere on the roots).

Roots grow at temperatures above 40F which means, among other things, that the roots of your deciduous tree are still growing after it is bare in the fall. After some time at temperatures below ca. 40F, the roots of conifers and deciduous trees become dormant. Roots can be combed and pruned safely any time while the tree is dormant. Were we to do this when the tree is actively growing, it would eliminate the root hairs and the tree will rapidly dessicate and likely die; possibly not if all the foliage is removed, but then the question is whether new buds can be made to refoliate or the tree simply runs out of carbohydrates with which to carry on the processes of living. At any rate, I think you can see a rationale for repotting before leaf out which is most commonly described as 'bud swell'.

Even though these principles also apply to conifers, their responses are slower and differ in many subtle ways. You will see drooping and withering foliage in a matter of days on deciduous trees when the roots are damaged. Conifers often take months to a year to show a similar response. This, IMHO, is what makes confers more challenging - there is a long time separation between cause and effect, unlike deciduous trees.

Still, there is much to be learned if you are interested. One of my emerging interests, for example, concerns 'dormancy' and safe times for repotting. All trees have growth rings. These appear because there is rapid xylem growth in the spring (known as early wood). Later the rate of adding xylem slows abruptly and the xylem lumens are smaller (late wood). So, what happens when the tree switches from early to late wood production? Does this correspond to a dormant period in August/September? If you do much gardening you'll know that August/September is a good time to transplant perennial stuff, like roses (even if it is not hotter than hell where you live). Vance Woods told the bonsai world many years ago that this is the best time (August/September) to repot Mugo pines. I repot my Mugo pines at this time and see that they thrive, just like Vance said they will. I cannot say that it is better than spring repotting, but it is more convenient for me to do Mugos in August/September than in the spring. Further, I haven't tried this on any other species, but I suspect that there is a period of pseudo-dormancy in all trees in these months and that that root work and repotting can also be done on most species. Aside from a little planning, all one needs is curiosity, investment in a number of cheap saplings, and some patience.

I suggest you read all the articles on the evergreengarendworks.com site and follow the leads from there to places like the Warnell School of Forestry and onto scholarly articles as your interests lead you. Bonsai is an art form that depends upon horticulture. Largely, bonsai is lore, but it works for the most part. Horticulture is highly scientific, but is devoted to commercial forrestry. There is a large gulf between the two, but both have growing trees in common. There is also a vast amount of biochemical research that I am finding to be most interesting. It might become interesting for you. Google/Bing/etc. is your friend.

I know you probably just wanted a sip and instead you got a fire hose! Sorry, but it is the season for excesses. Enjoy yours.

0soyoung wrote:Despite the descriptions of 'energy flow' that continue to be promulgated, all energy/food for the tree is manufactured by the foliage. Every branch makes enough carbohydrates for its own needs plus some for the roots and trunk. All the energy needed for deciduous trees to start up in the spring is stored as starches in the leaf buds. A bit more is stored in other (vascular cambium and ray parenchyma) living cells. In all trees, all food stored locally, even conifers. If you prune in dormancy, it does not change the energy storage in the rest of the tree.

Water and nutrients are drawn up the tree through the xylem (wood) by transpiration (i.e., it is sucked up the tree through the little xylem 'soda staws'). Therefore, if you remove all buds on a deciduous branch, it is dead because no leaves will emerge in spring to draw water and nutrients.

The basic phytohormone do-loop in trees is the foliage makes auxin that flows downward in the phloem to the roots. The roots make cytokinins that signal nitrogen is available and stimulate foliage growth. Auxin induces the cambium to make more xylem and phloem and to grow more roots. Auxin, however, also acts as a defoliant and deactivates 'down stream' buds closer to the trunk/roots. Pruning the apical foliage from a deciduous branch AFTER it has leafed out collapses the auxin flow and releases interior buds (causes back budding). Candle pruning and needle plucking similarly stimulate back budding in conifers because it collapses the auxin flow (though needle plucking is mostly for getting light to the interior of the tree to help stimulate bud release). The auxin and cytokinin levels are both low during dormancy, so pruning during dormancy has no direct back budding effect.

Trees effectively stop growing when the air temperatures are above ca. 95F because the tree burns more energy than can be captured by the foliage (respiration outpaces photosynthesis). Roots don't grow at temperatures above roughly 95F and begin to die at soil temperatures above 105F (supraoptimal root temperatures). Since something like 95% of the water drawn in by the roots is lost to transpiration, it is most important to keep your soil temperatures below 105F. Roots adsorb water and nutrients primarily through microscopic root hairs. Root hairs are elogations of individual cells on the surface of the root near the tip of the root. Each hair lasts for only a matter of days. New hairs are made as the root tip extends/advances. If the roots aren't growing there soon will be no hairs and the tree will get very sick if not die (there is weak absorption elsewhere on the roots).

Roots grow at temperatures above 40F which means, among other things, that the roots of your deciduous tree are still growing after it is bare in the fall. After some time at temperatures below ca. 40F, the roots of conifers and deciduous trees become dormant. Roots can be combed and pruned safely any time while the tree is dormant. Were we to do this when the tree is actively growing, it would eliminate the root hairs and the tree will rapidly dessicate and likely die; possibly not if all the foliage is removed, but then the question is whether new buds can be made to refoliate or the tree simply runs out of carbohydrates with which to carry on the processes of living. At any rate, I think you can see a rationale for repotting before leaf out which is most commonly described as 'bud swell'.

Even though these principles also apply to conifers, their responses are slower and differ in many subtle ways. You will see drooping and withering foliage in a matter of days on deciduous trees when the roots are damaged. Conifers often take months to a year to show a similar response. This, IMHO, is what makes confers more challenging - there is a long time separation between cause and effect, unlike deciduous trees.

Still, there is much to be learned if you are interested. One of my emerging interests, for example, concerns 'dormancy' and safe times for repotting. All trees have growth rings. These appear because there is rapid xylem growth in the spring (known as early wood). Later the rate of adding xylem slows abruptly and the xylem lumens are smaller (late wood). So, what happens when the tree switches from early to late wood production? Does this correspond to a dormant period in August/September? If you do much gardening you'll know that August/September is a good time to transplant perennial stuff, like roses (even if it is not hotter than hell where you live). Vance Woods told the bonsai world many years ago that this is the best time (August/September) to repot Mugo pines. I repot my Mugo pines at this time and see that they thrive, just like Vance said they will. I cannot say that it is better than spring repotting, but it is more convenient for me to do Mugos in August/September than in the spring. Further, I haven't tried this on any other species, but I suspect that there is a period of pseudo-dormancy in all trees in these months and that that root work and repotting can also be done on most species. Aside from a little planning, all one needs is curiosity, investment in a number of cheap saplings, and some patience.

I suggest you read all the articles on the evergreengarendworks.com site and follow the leads from there to places like the Warnell School of Forestry and onto scholarly articles as your interests lead you. Bonsai is an art form that depends upon horticulture. Largely, bonsai is lore, but it works for the most part. Horticulture is highly scientific, but is devoted to commercial forrestry. There is a large gulf between the two, but both have growing trees in common. There is also a vast amount of biochemical research that I am finding to be most interesting. It might become interesting for you. Google/Bing/etc. is your friend.

I know you probably just wanted a sip and instead you got a fire hose! Sorry, but it is the season for excesses. Enjoy yours.

Thanks. Actually, this was the kind of response I was looking for, something that gave a fairly in depth explanation of the process involved in plant growth. I'm going to check out those articles you linked.

I thought Vance re-pots mugos in late June in the northern states after the needles have fully extended, hardened and settled down. I believe this is mid-summer for him not really late summer dormancy time??

Of course, the problem with telling someone "the best" time to do anything with your trees is that the answer is "it depends:"

On the experience of the person who asks,

On the species of tree involved,

On where the tree is.

An "expert" can repot just about any time of year. A beginner (and most intermediate) grower probably ought to wait until spring "when the buds are swelling."

I'd guess that, if you have to ask, you should wait.

_________________Jim Lewis - lewisjk@windstream.net - Western NC - People, when Columbus discovered this country, it was plumb full of nuts and berries. And I'm right here to tell you the berries are just about all gone. Uncle Dave Macon, old-time country musician

there have been some excelent scientific/ factual points about plant responses in the thread but there are other factors to consider - the initial health of a tree is critical in its ability to recover from, or tollerate 'bonsai' work. root work on non dormant roots will not always be potentaillly critical to the tree either, some trees do not ever go dormant yet they are still used successfully as bonsai - pruned, repotted etc Even in my mild Cornish location chinese elms, satsuki etc can go through many winters non dormant - they are repotted 'in growth' through neccessity. Many collected tropicals end up with no roots and no branches or foliage so it proves the tree contains reserve energy to regenerate both at the same time too.

there is a relationship between roots and foliage and this is extremely variable between species too, not a simple black and white blanket rule for all species - some trees can recover, respond (or even thrive) after drastic root reduction if plenty of foliage is present - i'd put juniper in this category - other trees can respond well to total defoliation and total branch removal back to a bare trunk - trident maples for sure, satsuki too, so the rule of foliage being needed or essential is disproven instantly

the true answer is location is a factor, species you are working with is critical, but your skill with plant health prior to work and your skill in plant after care are the greatest deciding factors to your success rate.

marcus watts wrote:there have been some excelent scientific/ factual points about plant responses in the thread but there are other factors to consider - the initial health of a tree is critical in its ability to recover from, or tollerate 'bonsai' work. root work on non dormant roots will not always be potentaillly critical to the tree either, some trees do not ever go dormant yet they are still used successfully as bonsai - pruned, repotted etc Even in my mild Cornish location chinese elms, satsuki etc can go through many winters non dormant - they are repotted 'in growth' through neccessity. Many collected tropicals end up with no roots and no branches or foliage so it proves the tree contains reserve energy to regenerate both at the same time too.

there is a relationship between roots and foliage and this is extremely variable between species too, not a simple black and white blanket rule for all species - some trees can recover, respond (or even thrive) after drastic root reduction if plenty of foliage is present - i'd put juniper in this category - other trees can respond well to total defoliation and total branch removal back to a bare trunk - trident maples for sure, satsuki too, so the rule of foliage being needed or essential is disproven instantly

the true answer is location is a factor, species you are working with is critical, but your skill with plant health prior to work and your skill in plant after care are the greatest deciding factors to your success rate.

cheers, intersting thread

You make a good point, about the energy stored within the plant. The question for me now is, how would one go about utilizing the energy held within a branch they wish to remove?

It is, of course, gone from the tree once cut. The energy stored in the branch can be used in a cutting. Rooting hormone helps the cutting use some of that energy to form roots. Once roots form, the "natural" process starts again.

_________________Jim Lewis - lewisjk@windstream.net - Western NC - People, when Columbus discovered this country, it was plumb full of nuts and berries. And I'm right here to tell you the berries are just about all gone. Uncle Dave Macon, old-time country musician